Rays of sunlight include visible rays and besides rays in wavelength regions outside a visible region, i.e., ultraviolet rays and infrared rays. These ultraviolet and infrared rays are useless for human visual activity, or rather, their absence is often preferable to their presence in that the ultraviolet rays have chemical action and the infrared rays have thermal action.
For example, it is indicated that the ultraviolet rays form the causes of sunburn of the skin and of cutaneous aging and cancer to the human body. It is also indicated that they cause deterioration such as reduction in strength, discoloration and fading to plastic products, rubber products, synthetic fibers and other various products.
On the other hand, the infrared rays raise the temperatures within rooms of houses and the like and reduce the cooling efficiency of air conditioners and the like in a season high in air temperature, for example, the summer season, so that energy is wasted.
For example, agricultural greenhouse facilities are constructed by covering a plantation atmosphere with a covering material. However, any covering material used heretofore is not particularly designed as to performance that rays within a particular wavelength region are selectively absorbed or transmitted. Therefore, in greenhouse facilities using such a covering material, a working environment within the facilities is worsened by ultraviolet rays, and articles placed therein are also deteriorated. In addition, the interiors of the facilities are heated to considerably high temperatures by infrared rays during a season high in air temperature. Therefore, they cannot be used in cultivation of the crops, in particularly, the crops which are apt to be easily damaged by high temperatures.